The present invention involves a well packer and associated tools and more specifically is directed towards an hydraulically actuated well packer actuatable after the well head has been flanged up, and featuring a releasable contraction means for compensation against thermal constraction and expansion of the tool string in response to the wide range of temperatures from the ground surface to the bottom of the well bore, and particularly advantageous in compensating for the large contraction of the string encountered when very cold fluids are pumped down the well from the surface.
When working in extremely cold regions, such as Alaska and the north slope, wide ranges of temperatures are often encountered between surface conditions and bottom hole location. For instance, a well may have a bottom hole temperature of 200.degree. to 300.degree. F, while at the surface the ambient temperature may approach 80.degree. below zero. As a consequence of this, the thermal contraction and expansion of a steel tubing string 10,000 to 20,000 feet in length going from the surface into the well bore accumulates into a considerable amount while the string is located downhole.
There are several extremely efficient and dependable packer mechanisms available for use under normal temperature conditions which suffer some disadvantages when used in cold climates. For example, the packers disclosed in U.S. Pat. Nos. 3,548,936 and 3,818,987, assigned to Dresser Industries, Inc. and commercially designated as Uni-Packer VII well packers and Uni-Packer VIII well packers, are particularly advantageous for use in well bores where mechanical and/or hydraulic setting is required.
The hydraulic actuation of the packers is achieved by a combination of mechanical tension and hydraulic pressurization. Although this is acceptable in the majority of the cases, under the present conditions of extreme temperature ranges and the desirability to close in the well before setting the packer, it is necessary to utilize a packer assembly that is totally actuatable by hydraulic pressure and which is retrievable by wire line or tubing retrieval tools.
It is also desirable to utilize a packer assembly with a thermal contraction mechanism for absorbing the large cumulative contraction of the tubing string resulting from the extremely cold conditions experienced by the string in the hole when cold fluids are pumped down the string or the annulus. The only practical method of providing such a joint lies in utilizing a lengthy sliding telescoping joint, which telescoping joint may be temporarily locked into a ridged configuration while going in the well to allow manipulation of the well tools and placement within the proper location in the well as well as traversing binding conditions in the casing.
The problem lies in providing a locking mechanism in the sliding expansion joint which will withstand various shocks and abuse while going in the hole and yet which can be actuated after the well head has been flanged up. The prior art devices commonly utilized for the releasing of the telescoping expansion joint, utilize such means as a rotational threaded release, heavy shear pins, a wire line trip release, or a ball and seat combination to introduce the telescopic action into the tubing string.
The present invention solves these difficulties by providing a packer mechanism that is fully hydraulically actuatable yet which may be retrieved easily by wire line or tubing retrieval and which also features a full telescoping thermal joint having release means also total actuatable by hydraulic pressure. Thus, the mechanism of this invention may be run in on a tubing string, the well head flanged up, and then actuation of the packer and the thermal joint accomplished with a closed-in well head.